* fix(api): forward real LLM usage in /v1/chat/completions response
_chat_completion_response() hardcoded prompt_tokens/completion_tokens
to zero. Now reads agent_loop._last_usage (set by process_direct
after every LLM call) and forwards the actual prompt/completion counts.
Streaming path is unchanged; usage is only surfaced in non-streaming
responses for now.
Fixes#4309
* fix: use defensive getattr for _last_usage and add it to all test mock agents
- Use getattr(agent_loop, '_last_usage', None) in server.py for safety
- Add _last_usage = {} to mock agents in test_api_attachment.py and test_api_stream.py
- Prevents AttributeError/500 when mock agents don't have the attribute
* fix(api): preserve provider total usage
---------
Co-authored-by: michaelxer <michaelxer@users.noreply.github.com>
Co-authored-by: Xubin Ren <52506698+Re-bin@users.noreply.github.com>
The streaming API currently logs backend exceptions but still emits the
same `finish_reason: "stop"` + `[DONE]` terminator used for successful
responses. That makes a failed streamed request look successful to
OpenAI-compatible clients.
This keeps the fix narrow: track whether the stream backend failed and
suppress the success terminator in that case. A regression test locks in
the expected behavior.
Constraint: Keep the non-streaming response path untouched
Constraint: Follow up on the known limitation called out during PR #3222 review without redesigning the SSE protocol
Rejected: Introduce a custom SSE error event shape in the same patch | expands API surface and review scope
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: If explicit streamed error events are added later, keep them distinct from the success stop+[DONE] terminator to preserve client retry semantics
Tested: PYTHONPATH=$PWD pytest -q tests/test_api_stream.py /Users/jh0927/Workspace/nanobot-validation-artifacts-2026-04-18/test_api_stream_error_regression.py
Not-tested: Full repository test suite
Related: #3260
Related: #3222
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